Image formation method and apparatus

ABSTRACT

An image formation method for forming an image containing an embossed portion of an expandable material on a recording medium, comprising converting height information about an embossed image which is the image of the embossed portion to the same density information as one used to indicate a density of a non-embossed image which is not raised, and controlling an amount of the expandable material formed on the recording medium according to the converted density information.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image forming method and apparatuswhich use an expandable material to form an embossed image, and moreparticularly to an image formation method and image formation apparatuswhich can easily and simply form a desired embossed image by convertingheight information on the embossed image to density information whichindicates a density of a non-embossed image and controlling an amount ofan expandable material which is transferred onto a recording mediumaccording to the converted density information.

2. Description of the Related Art

Conventionally, an image formation apparatus such as a printer or a copymachine which adopts an electrophotographic method or an electrostaticrecording method forms flatly an image such as characters, figures,photographs or the like in black and white or full color on a recordingmedium such as a recording sheet, and the formed image is visuallyrecognized and used as a desired information conveying unit.

Meanwhile, it is demanded in recent years to provide a method which canconvey to a third party not only visually flat information by an imageformed on a recording medium but also a variety of information byaddition of three-dimensional information based on shadows produced byvertical intervals of the image or the touch with fingers.

As a method to add three-dimensional information to the image, there isa method to form the image as a three-dimensional embossed image.

The method of forming an embossed image has been devised in variousways, and a variety of techniques have been proposed.

For example, as a method of producing a pamphlet or the like having anembossed image, there is a method to form an embossed image by printingan ultraviolet-curing type high-viscosity polymer ink into a raised formby a printing technique such as ordinary silk-screening and curing byirradiating ultraviolet rays to form an embossed image, but such amethod cannot be easily used by an ordinary office or a public facility.

Japanese Patent Application Laid-Open Publication No. 52-28325 proposesa toner for electrophotography containing a dry expandable agent.

This toner for electrophotography containing a dry expandable agent is atoner which has a conventional toner and the dry expandable agent mixedin powder form and can be used to obtain an embossed image by forming animage and expanding the dry expandable agent by heating.

But, some powder mixture cannot have the toner and the expandable agentmixed uniformly and adequately, the expandable agent not having anadhesive power is often on the interface with paper, and an embossedimage having an adequate fixing property cannot be obtained.

Japanese Patent Application Laid-Open Publication No. 7-061047 proposesan information input/output method for forming a projection image byusing a toner containing a heat-sensitive expanding agent.

The toner used for the above method is produced by mixing and finelypulverizing a binder resin for a toner, a coloring agent and aheat-sensitive expanding agent. The pulverized toner has theheat-sensitive expanding agent revealed on its surface.

Therefore, the heat-sensitive expanding agent is exposed on theinterface between paper and the toner. The adhesion between the tonerand the paper is degraded in the same way as the above-describedproposition, and the obtained image has a degraded fixing property.

Because the heat-sensitive expanding agent is exposed to the tonersurface, the toner surface has a nonuniform electrostatic property.Therefore, the toner has a wide distribution of electrification, andwhen the toner is used under low-temperature and low-humidityenvironments or for a long period, the image has fogging or the like,and image quality is degraded.

Besides, because the used toner is produced by an ordinary kneading andpulverizing method, it is considered that the heat-sensitive expandingagent is mostly expanded by heating at the time of kneading and itseffect is lost.

As a result, the expanding agent cannot expand sufficiently whenthermally fixed only by an ordinary copy machine or the like. It isnecessary to additionally pass the output image through an overheatingdevice. It is insufficient in terms of simplicity and easiness.

Therefore, the present applicant has already proposed a novel imageforming toner which can be used to easily form an embossed image by acommon copy machine or a printer and an image formation apparatus usingthe above image forming toner (Japanese Patent Application Laid-OpenPublication No. 2000-131875 and Japanese Patent Application Laid-OpenPublication No. 2001-134006).

The image formation apparatus according to Japanese Patent ApplicationLaid-Open Publication No. 2000-131875 is configured in such a way thatthe toner contains at least a binder resin and an expanding agent, thetoner does not substantially have the expanding agent exposed to thetoner surface, and the expanding agent contained in the toner isexpanded by a fixing unit to form an embossed image on a recordingmedium. Thus, by using the toner containing the binder resin and theexpanding agent, an embossed image can be formed on a recording medium.

The image formation apparatus according to Japanese Patent ApplicationLaid-Open Publication No. 2001-134006 uses a toner which contains atleast a binder resin and an expanding agent. To fix the toner imageformed with the toner on a recording medium by a fixing unit, theexpanding agent contained in the toner is expanded by the fixing unit toform the embossed image on the recording medium, and the fixed tonerimage has an image structure in which the expanding agent has at leasttwo layers of expanded gas bubble. After the thermal fixing processing,an embossed image having adequate height and durability can be formed.

Japanese Patent Application Laid-Open Publication No. 2000-131875 andJapanese Patent Application Laid-Open Publication No. 2001-134006 areeffective as techniques to realize an embossed image. But, they do notdisclose a method of designating height information to actually give upsand downs to a print such as a map, graphics, a photograph image or thelike and a method of forming an embossed image from image data.

Under the circumstances described above, the present invention providesan embossed image formation apparatus and embossed image informationmethod which can easily form an embossed image desired by the user.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above circumstancesand an aspect of the present invention is an image formation method forforming an image containing an embossed portion of an expandablematerial on a recording medium, comprising: converting heightinformation about an embossed image which is the image of the embossedportion to same density information as one used to indicate a density ofa non-embossed image which is not raised; and controlling an amount ofthe expandable material formed on the recording medium according to theconverted density information.

Another aspect of the present invention is an image formation method forforming an image containing an embossed portion of an expandablematerial on a recording medium, comprising: converting heightinformation about an embossed image which is the image of the embossedportion to same density information as one used to indicate a density ofa non-embossed image which is not raised; and sending the converteddensity information to an image formation apparatus which controls anamount of the expandable material formed on the recording mediumaccording to the density information.

Still another aspect of the present invention is an image formationapparatus for forming an image containing an embossed portion of anexpandable material on a recording medium, comprising: a conversion unitwhich converts height information about an embossed image which is theimage of the embossed portion to same density information as one used toindicate a density of a non-embossed image which is not raised; and acontrol unit which controls an amount of the expandable material formedon the recording medium according to the density information convertedby the conversion unit.

According to the present invention, it is possible to form an embossedimage, whose height on a recording medium is controlled, by an ordinaryelectrophotographic type copy machine, a small printer or the like.

As used in the specification and claims herein, the word “embossedimage” refers to an image having a three-dimensional appearance.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the present invention will be described indetail based on the following figures, wherein:

FIG. 1 is a block diagram showing a structure of the main components ofan image formation apparatus according to the present invention;

FIG. 2A to FIG. 2C are conceptual sectional views illustratingtransferring and fixing processes by the image formation apparatus shownin FIG. 1 and a formed image;

FIG. 3A to FIG. 3C are structure diagrams of Table 1, Table 1′ and Table1″ showing corresponding relationships among height ratio T %, thermalexpandable toner amount H and thermal expandable toner density H %;

FIG. 4 is a graph showing a corresponding relationship among the heightratio T %, the thermal expandable toner amount H and the thermalexpandable toner density H %; and

FIG. 5 is a structure diagram of Table 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will be described with reference tothe accompanying drawings.

FIG. 1 is a block diagram showing a structure of the main components ofthe image formation apparatus according to the present invention.

This image formation apparatus is used as, for example, a color printerof an electrophotographic type.

It is to be understood that FIG. 1 shows an example of embodiments ofthe present invention, and the invention is not limited to it.

As shown in FIG. 1, an image formation apparatus 100 according to thepresent invention is mainly comprised of an image processing section 1and an image forming section 2.

The image processing section 1 has a color space conversion section 11which performs gamma correction of image data (including, e.g., an sRGBimage signal of red (R), green (G), blue (B) and a user-designatedheight information signal) input from an unshown personal computer orthe like to convert into an independent color space which does notdepend on a device, thermal expandable toner density conversion section12 which sets an amount of a thermal expandable toner of the input imagedata according to the user-designated height information (e.g.,brightness is designated when an image having a height of an embossedimage controlled according to brightness of the input image data isformed), a color correction section 13 and a gradation correctionsection 14 which produce four original color material gradation data onyellow (Y), magenta (M), cyan (C) and black (K) (8 bits each) andexpandable toner gradation data (expandable toner amount information) toshow colors by a printer, and a drawing section 15 which produces imageformation data for driving exposure devices 20Y to 20H of the imageforming section 2 and outputs the image formation data to the imageforming section 2.

The image forming section 2 has the exposure devices 20Y to 20H whichcontrol light exposure of photoconductors 24Y to 24H by laser beam LBaccording to the image formation data which is image-processed andtransmitted by the image processing section 1, electrizing devices 21Yto 21H which previously change the surfaces of the photoconductors 24Yto 24H to a prescribed polarity (e.g., negative polarity), developingdevices 23Y to 23H which develop latent images formed on the surfaces ofthe photoconductors 24Y to 24H with a toner to form toner images T, anintermediate transfer unit 29 which is disposed below thephotoconductors 24Y to 24H and transfers the toner images T formed onthe photoconductors 24Y to 24H, a fixing device 203 which fixes thetoner images T of the intermediate transfer unit 29 onto a recordingmedium 200.

The exposure devices 20Y to 20H modulates an unshown semiconductor laseraccording to the original reproduction coloring material gradation datainput from the image processing section 1 and emits the laser beam LB tothe photoconductors 24Y to 24H to scan and expose them.

The photoconductors 24Y to 24H are driven to rotate in an arrowdirection at a prescribed speed by an unshown drive unit.

The surfaces of the photoconductors 24Y to 24H are previously chargeduniformly by corona electrizers of electrizing devices 21Y to 21H andexposed to and scanned by the laser beam LB according to the originalreproduction coloring material gradation data to form electrostaticlatent images.

When the developing devices 23Y to 23H are used for a full colormachine, developers of yellow (Y), magenta (M), cyan (C), black (K) andwhite (H: thermal expandable toner) are introduced into them.

Here, all of the developers stored in the developing devices 23Y to 23Hmay be developers which mainly consist of the thermal expandable tonerof the present invention or at least one or two or more colors may beprovided by the developers which mainly consist of thermal expandabletoner of the present invention.

According to the colors of an image to be formed, the toner images T ofall or part of the five colors of yellow (Y), magenta (M), cyan (c),black (K) and white (H: thermal expandable toner) to be formed on thephotoconductors 24Y to 24H are transferred onto the surfaces of theintermediate transfer unit 29 in a state sequentially multiplied byprimary transfer rolls 25Y to 25H.

The toner image T which is formed by sequentially superimposing andtransferring onto the intermediate transfer unit 29 is applied with abias of an opposite polarity from a frictional electric charge of thetoner by a secondary transfer roll 27 and, transferred onto therecording medium 200.

The intermediate transfer unit 29 has a drive roll 28 and a driven roll26, and the driven roll 26 is disposed as a roll opposite to thesecondary transfer roll 27.

The intermediate transfer unit 29 is supported to rotate in an arrowdirection at the same moving speed as the peripheral speeds of thephotoconductors 24Y to 24H.

The toner image T transferred onto the intermediate transfer unit 29 istransferred onto the recording medium 200 in prescribed timing.

The toner images T having the prescribed colors are collectivelytransferred from the intermediate transfer unit 29 onto the recordingmedium 200 by the driven roll 26 and the secondary transfer roll 27 asdescribed above.

The toner images T collectively transferred onto the recording medium200 are transported to the fixing device 203 and fixed onto therecording medium 200 by being heated and pressed by means of a heatingroll 201 and a pressure roll 202 disposed in the fixing device 203.

In the area where the thermal expandable toner of the collectivelytransferred toner images T is transferred, the thermal expandable toneris thermally expanded by being heated by the fixing device 203 to forman embossed image.

The image formation apparatus 100 of the present invention controls anamount of the thermal expandable toner (H) according to the inputimage's height information designated by the user to form the embossedimage whose height is controlled according to the designated heightinformation.

FIG. 2A to FIG. 2C are conceptual sectional diagrams for illustratingtransferring and fixing processes by the image formation apparatus 100and a method of forming the embossed image according to the presentinvention.

As shown in FIG. 2A, the toner images T of all or part of five colors ofyellow (Y), magenta (M), cyan (C), black (K) and white (H: thermalexpandable toner) to be formed on the photoconductors 24Y to 24H shownin FIG. 1 according to the colors of the image to be formed aretransferred onto the intermediate transfer unit 29 in a statesequentially superimposed by the primary transfer rolls 25Y to 25H.

As shown in FIG. 2B, the toner images T sequentially superimposed andtransferred onto the intermediate transfer unit 29 (see FIG. 2A) arecollectively transferred onto the recording medium 200 (FIG. 2B, 210:unfixed color toner image) by applying a bias having an oppositepolarity from a toner electric charge to the secondary transfer roll 27.

The unfixed color toner images T (FIG. 2B, 210: unfixed color tonerimage) collectively transferred onto the recording medium 200 aretransported to the fixing device 203 and pressed and heated by theheating roll 201 and the pressure roll 202 disposed in the fixing device203 and fixed onto the recording medium 200 (FIG. 2C, 220: fixed colortoner image).

As shown in FIG. 2C, the fixed color toner image 220 formed by the imageformation apparatus 100 of the present invention forms an embossed colorimage by thermal expansion of the toner image in the area where thethermal expandable toner (H) image is transferred.

Embodiment 1 according to the present invention converts the respectivepixel areas of the input image into density information about thethermal expandable toner according to the height information (colorbrightness of image data) designated by the user and controls an amountof the thermal expandable toner according to the density information toform the embossed color image having the desired height and colorationon the recording medium.

As shown in FIG. 1, the image processing section 1 of the imageformation apparatus 100 according to the present invention has the colorspace conversion section 11, the thermal expandable toner densityconversion section 12, the color correction section 13, the gradationcorrection section 14 and the drawing section 15.

Image data (containing, e.g., an sRGB image signal of red (R), green (G)and blue (B) and a user-designated height information (color brightness)signal) input from an unshown personal computer or the like is input tothe color space conversion section 11.

Generally, the color brightness is indicated by a value of L* in anL*a*b* color space which does not depend on the device.

Accordingly, the color space conversion section 11 performs gammacorrection of the input image data (sRGB) signal, converts the convertedRGB value to a value of an XYZ color space which is independent of thedevice and converts to a value of the L*a*b* color space (CIE1976).

Brightness of the input image data (sRGB) signal can be obtained byconverting the input image data (sRGB) signal to a value of the L*a*b*color space and calculating a value of L*.

The conversion from the RGB value to the value of the XYZ color spacecan be determined by using, for example, the following conversionexpressions.

X=0.4124×R+0.3576×G+0.1805×B

Y=0.2126×R+0.7152×G+0.0722×B

Z=0.0190×R+0.1192×G+0.9505×B

The conversion from the value of the XYZ color space to the value of theL*a*b* color space can be determined by, for example, the followingconversion expressions.

The value of L* is converted by using the following conversionexpressions:

 L*=116x(Y/Yw)^((1/3))

when (Y/Yw)>=0.008856, and

L*=903.29×(Y/Yw)

when (Y/Yw)<0.008856.

Values of a* and b* are converted by using the following conversionexpressions.

a*=500x(xx−yy)

b*=200x(yy−zz)

In the above conversion expression of a* and b*,

when (X/Xw)>=0.008856,

it is xx=(X/Xw)^((1/3));

when (X/Xw)<0.008856,

it is xx=7.787xX/Xw+16/116;

when (Y/Yw)>=0.08856,

it is yy=(Y/Yw)^((1/3));

when (Y/Yw)<0.008856,

it is yy=7.787xY/Yw+16/116;

when (Z/Zw)>=0.008856,

it is zz=(Z/Zw)^((1/3)); and

When (Z/Zw)<0.008856,

it is zz=7.787×Z/Zw+16/116.

In the above expressions, Xw, Yw and Zw indicate the respective valuesof white points in the XYZ color space.

By using the above conversion expressions, the signal of input imagedata (sRGB) can be converted to the value of the L*a*b* color space.

In the color space conversion section 11, the input image data isconverted to the value of L*a*b* for each pixel area and input to thethermal expandable toner density conversion section 12 together with theconverted value of L*a*b* and the converted height information (colorbrightness).

The thermal expandable toner density conversion section 12 calculates aheight ratio T % of the brightness L* value of each pixel area of theinput image data according to the L*a*b* values of the input image dataconverted by the color space conversion section 11 and the convertedheight information (color brightness).

The height ration T % here indicates the brightness L* (e.g., L* 1)value having the input image data on each pixel area converted to theL*a*b* color space in percentage (%) against a range (e.g., L*0 to L*n)of an actual value of brightness L* of the color in the L*a*b* colorspace.

For example, when it is assumed that the value of L* of each pixel areaof the input image data is L*1 and a range of the actual value of thebrightness L* in the L*a*b* color space is L*0 to L*n, the height ratioT % 1 (percentage) of the brightness L*1 value of the input image datais calculated by T %1=((L*1−L*0)/(L*n−L*0))×100.

Table 1 in which the height ratio T %, the thermal expandable toneramount H and the thermal expandable toner density H % are correspondedwith one another is stored in the thermal expandable toner densityconversion section 12, and the input image data is converted to thevalue of the L*a*b* color space by the color space conversion section11, and the thermal expandable toner amount H and the thermal expandabletoner density H % corresponding to the height ratio T % of the convertedL* value can be calculated from Table 1.

Here, the thermal expandable toner density indicates the same densityvalue as that used to indicate the density of a non-embossed image whichis not raised. This density is indicated according to an area gradationmethod on the recording medium.

When the thermal expandable toner is formed on the recording mediumaccording to the density value, the density does not actually change butthe height changes.

FIG. 3A to FIG. 3C are structure diagrams of Table 1, Table 1′ andTable″ which show corresponding relationships among the height ratio T%, the thermal expandable toner amount H and the thermal expandabletoner density H %.

As shown in FIG. 3A, for example, when it is assumed that an input imagedata (sRGB) signal of each pixel area is converted to a value of theL*a*b* color space by the color space conversion section 11 and theheight ratio T % of brightness L* of the input image data signal iscalculated as “70”(%) from the converted L*a*b* values by the thermalexpandable toner density conversion section 12, “70”(%) is searched inthe left column of the value of T % in Table 1 to find the thermalexpandable toner amount H of “H30” in the middle column and the thermalexpandable toner density H % of “30”(%) in the right columncorresponding to the T % value “70”(%).

Thus, the height ratio T % is calculated according to the colorbrightness from the input image data signal, and the thermal expandabletoner density H % and the thermal expandable toner amount Hcorresponding to each of brightness can be calculated with ease.

For example, Table 1 can be previously produced by the followingprocedure.

First, input image data for output of a patch (test print) is prepared.

From this input image data for patch output, a patch is output whilevarying the thermal expandable toner amount H from 0 by a prescribedamount ΔH by using the image formation apparatus 100 according to thepresent invention, and height T of the patch-output embossed image ismeasured.

In a range that the patch-output embossed image can be adequatelyrecognized and a fixing property is sufficient in practical use, acorresponding relationship between the thermal expandable toner amount Hand the height T of the embossed image is graphed according to themeasured result.

As shown in FIG. 4, a characteristic graph A of the embossed imageheight T corresponding to the thermal expandable toner amount H isprepared by taking the thermal expandable toner amount H on horizontalaxis 40 and the embossed image height T on vertical axis 41.

This characteristic graph A is prepared by plotting the value of theembossed image height T with respect to each thermal expandable toneramount H while changing the thermal expandable toner amount H from 0 bya prescribed amount ΔH and performing linear interpolation or the like.

The characteristic graph A has the embossed image height T as T0 whenthe thermal expandable toner amount H is 0 (H0), and the thermalexpandable toner amount H as Hm when the embossed image height T ismaximum (Tm) in a range that the patch-output embossed image isadequately recognizable and a fixing property is also adequate inpractice.

It is assumed that the vertical axis 41 (embossed image height T) andthe horizontal axis 40 (thermal expandable toner amount H) of thecharacteristic graph A prepared by the above-described procedure are100% when the embossed image height T is maximum (Tm), the thermalexpandable toner amount Hm at that time is 100%, H0 is 0% when thethermal expandable toner amount is 0, and the embossed image height T0is 0% at that time. And, a graph with the addition of a vertical axis 43(height ratio T %) and a horizontal axis 42 (thermal expandable tonerdensity H %) having 0% to 100% graduated at regular intervals isprepared.

According to the above-described method, the corresponding relationalgraph of the thermal expandable toner amount H (horizontal axis 40) andthe embossed image height T (vertical axis 41) can be converted to thecorresponding relational graph of the height ratio T % (vertical axis43) and the thermal expandable toner density H % (horizontal axis 42).

For example, it is assumed that the corresponding relationship among theheight ratio T % of the embossed image formed on the recording medium200, the thermal expandable toner amount H and the thermal expandabletoner density H % is obtained as indicated by the graph A, graph B andgraph C of FIG. 4 by the above-described procedure.

Then, according to the corresponding relationship of the graph A, whenan image is to be formed with the height ratio T % of “70”(%), thethermal expandable toner density H % is “30”(%), and the thermalexpandable toner amount H at that time is converted to “H30”. Thus, theimage having the target height can be obtained.

According to the corresponding relationship of the graph B, when animage is desired to be formed with the height ratio T % of “50”(%), thethermal expandable toner density H % is “50”(%), and the thermalexpandable toner amount H at that time is converted to “H50”. Thus, theimage having the target height can be obtained.

According to the corresponding relationship of the graph C, when animage is desired to be formed with the height ratio T % of “40”(%), thethermal expandable toner density H % is “80”(%), and the thermalexpandable toner amount H at that time is converted to “H80”. Thus, acorresponding relationship to obtain the image with the target heightcan be obtained.

The tables prepared according to the characteristic graphs A, B and Cwhich indicate the corresponding relationships among the height ratio T%, the thermal expandable toner amount H and the thermal expandabletoner density H % are Table 1, Table 1′ and Table″ as shown in FIG. 3.

According to the above tables, the thermal expandable toner density H %and the thermal expandable toner amount H corresponding to theuser-designated color brightness (height information) can be determinedfrom the input image data.

The values of thermal expandable toner amount H and thermal expandabletoner density H % calculated according to the brightness (L*) value ofthe input image data by the thermal expandable toner density conversionsection 12 and the L*a*b* values are input to the color correctionsection 13.

The color correction section 13 produces a signal of YMCKH % from thethermal expandable toner amount H and the thermal expandable tonerdensity H % value input from the thermal expandable toner densityconversion section 12 and the L*a*b* values.

The color correction section 13 stores Table 2 which is used tocalculate a color correction conversion coefficient to be used for colorcorrection of the embossed color image.

FIG. 5 is a structure diagram of Table 2.

As shown in FIG. 5, Table 2 stores color correction conversioncoefficients used to generate the signal of YMCKH % from the signal ofL*a*b*.

Specifically, Table 2 is a table to correspond L*a*b* with YMCKH %(color correction conversion coefficient: coloration information)according to which, when a value in the left column of Table 2 isL*a*b*, a color correction conversion coefficient of a value of YMCKH %in the right column corresponding to the L*a*b* values is used toperform color correction, so that desired coloration of the embossedcolor image according to the expandable toner density H % formed at thattime can be obtained.

In Table 2, H % values “H %0”, “H %1”, “H %2”, . . . “H % m” are valuesof thermal expandable toner density H % calculated by the thermalexpandable toner density conversion section 12.

In other words, the thermal expandable toner amount H and the thermalexpandable toner density H % are calculated by the thermal expandabletoner density conversion section 12 according brightness L* designatedby the user from the input image data, and the YMCKH % value isdetermined from the calculated thermal expandable toner amount H andthermal expandable toner density H % and the L*a*b* values.

For example, Table 2 can be previously prepared according to thefollowing procedure.

First, this image processing device 100 is used to previously vary theexpandable toner density H % from 0% to 100% by a prescribed amount ΔH %so to output a CMYK signal set to the image forming section 2 and toperform patch output.

As shown in Table 1, Table 1′ and Table″ of FIG. 3, when the value ofthermal expandable toner density H % is determined, the value of thermalexpandable toner amount H is uniquely defined.

Therefore, when the thermal expandable toner density H % is varied from0% to 100% by a prescribed amount Δ H %, the thermal expandable toneramount H is discharged according to the thermal expandable toner densityH %.

Then, the output patch is measured for color to generate a deviceproperty transmission model which corresponds the L*a*b* value with theCMYKH % value.

An algorithm to prepare the device property transmission model includesvarious methods such as a neural network, a multiple regression method,Neugebauer theoretical formula and the like, and no particular method isdesignated.

Then, DLUT (LUT for three-dimensional color correction) indicating thecorrespondence between the L*a*b* value and the CMYKH % value isprepared.

To prepare the DLUT, a K value is determined from the L*a*b* value by aUCR (black generation/under color removal) processing corresponding tothe expandable toner density H %, and the CMYK value is determined fromthe K value and the expandable toner density H %.

In other words, inverse mapping is performed with the K value and the H% value of the device property transmission model determined by theabove-described patch color measurement stored.

When color correction is performed using a color correction conversioncoefficient (YMCKH %) corresponding to the L*a*b* values from the deviceproperty transmission model produced by the above-described procedure,an embossed color image having the desired height and coloration can beproduced by using the expandable toner density H % corresponding tobrightness (L*) of the input image signal.

Such relationships are stored in Table 2.

The color correction section 13 generates signals of L*a*b* value and H% value from the values of the thermal expandable toner density H % andthe L*a*b* values input from the thermal expandable toner densityconversion section 12 and uses Table 2 to perform color correction bycalculating a YMCKH % value in the right column corresponding to theL*a*b*H % value in the left column of Table 2.

Specifically, the L*a*b* values input from the thermal expandable tonerdensity conversion section 12 are used as a first key and the value ofthermal expandable toner density H % is used as a second key to retrievethe L*a*b*H % value in the left column of Table 2, and a conversioncoefficient (YMCKH % value) for color correction in the right columncorresponding to the L*a*b*H % value is read.

The read color correction conversion coefficient (YMCKH % value) and theL*a*b*H % value are calculated (e.g., multiplication) to perform colorcorrection.

The signal (Y, M, C, K, H %) undergone the color correction by the colorcorrection section 13 is subject to gradation correction by thegradation correction section 14, image formation data for driving theexposure devices 20Y to 20H of the image forming section 2 is producedby the drawing section 15, and the image formation data is output to theimage forming section 2.

In the image forming section 2, the thermal expandable toner density H %is calculated according to brightness (L*) of the input image data inputfrom the image processing section 1, the toner image is transferred ontothe recording medium 200 by the above-described method according to theimage data (Y, M, C, K, H %: gradation data) undergone the colorcorrection, and the transferred toner image is thermally fixed to therecording medium 200 to form an embossed image.

Thus, in Embodiment 1, the expandable toner density H % is determinedaccording to the brightness (L*) of the input image data (sRGB), and anembossed color image having desired height and coloration is formed.

The user-designated height information is determined to be brightness(L*) in Embodiment 1, but the brightness (L*) may be replaced withpsychometric chroma coordinates (a*(red-green color)) or psychometricchroma coordinates (b* (yellow-blue color)).

The psychometric chroma coordinates (a*) indicate red as a positivenumber of the a* value becomes larger in the L*a*b* color space andgreen as a negative number becomes larger, and the psychometric chromacoordinates (b*) indicate yellow as a positive number of the b* valuebecomes larger in the L*a*b* color space and blue as a negative numberbecomes larger.

In other words, the expandable toner density H % may be determinedaccording to coloration (a*) of the red-green color or coloration (b*)of the yellow-blue color of the input image data (sRGB) to form anembossed color image having desired height and coloration.

The above description is the same as in Embodiment 1 except that thevalue of brightness (L*) of the input image data (sRGB) is replaced withthe value of (a*(red-green color)) or the value of (b*(yellow-bluecolor)).

Embodiment 2 according to the present invention determines theexpandable toner density H % according to luminance (Y) the input imagedata (sRGB) to form an embossed color image having desired height andcoloration.

In order to determine luminance (Y) of the input image data (sRGB),Embodiment 2 converts the input image data on each pixel area to a valueof the XYZ color space independent of the device and determines theexpandable toner density H % according to the value of luminance (Y) ofthe value of the converted XYZ color space to form an embossed colorimage having desired height and coloration.

Embodiment 2 is the same as Embodiment 1 except that the signal of theinput image data (sRGB) is converted to the XYZ value of the XYZ colorspace independent of the device and the height ratio T % of Y value(luminance) of the converted XYZ value is calculated. Therefore, forconvenience's sake of explanation, the procedure that the input imagedata (sRGB) is converted to the XYZ value of the XYZ color space and theheight ratio T % of Y value (luminance) of the converted XYZ value iscalculated will be described with reference to FIG. 1.

The input image data (sRGB) on each pixel input from an unshown personalcomputer or the like is converted to the value of the XYZ color space bythe color space conversion section 11, and the converted XYZ value andthe height information (luminance) on the embossed image are input tothe thermal expandable toner density conversion section 12.

In the thermal expandable toner density conversion section 12, aluminance (Y) value of the input image data on each pixel area to arange (e.g., Y0 to Yn) of the value which can be actually possessed bythe height information (luminance) about the embossed image iscalculated in percentage (height ratio T %) according to the value ofXYZ of the input image data converted by the color space conversionsection 11 and the height information (luminance Y) about the embossedimage.

For example, when it is assumed that the value of Y is Y1 in a range ofY0 to Yn of the value which can actually be possessed by the heightinformation (luminance Y) about the embossed image, the height ratio T %1 of luminance Y can be calculated as follows.

T %132 ((Y1−Y0)/(Yn−Y0))×100

The thermal expandable toner density conversion section 12 stores, forexample, Table 1 as shown in FIG. 3A which corresponds the height ratioT % with the thermal expandable toner density H %. And, the thermalexpandable toner density H % corresponding to the height ratio T % ofthe luminance Y value calculated by Table 1 is calculated.

When the height ratio T % of luminance Y is calculated, the subsequentprocessing is the same processing as in Embodiment 1 and determines thethermal expandable toner density H % according to luminance (Y) of theinput image data (sRGB), and an embossed color image having desiredheight and coloration can be formed.

Embodiment 3 according to the present invention determines theexpandable toner density H % according to color difference of the inputimage data (sRGB) to form an embossed color image having desired heightand coloration. Generally, color difference ΔE* indicates a differenceof two colors quantitatively and can be indicated by a distance betweentwo points in a uniform color space.

Embodiment 3 is the same as Embodiment 1 except that in the thermalexpandable toner density conversion section 12 of Embodiment 1, thevalue of color difference ΔE* is calculated from a white point of theinput image data, and the height ratio T % of the calculated colordifference ΔE* value is determined.

A procedure until the color difference ΔE* from the white point of theinput image data (sRGB) and the height ratio T % of the color differenceΔE* are calculated will be described with reference to FIG. 1.

The input image data (sRGB) on each pixel input from an unshown personalcomputer is converted to the value of the L*a*b* color space by thecolor space conversion section 11, and the converted L*a*b* values andthe height information (color difference) about the embossed image areinput to the thermal expandable toner density conversion section 12.

The thermal expandable toner density conversion section 12 calculatesthe color difference ΔE* (e.g., color difference from the values ofwhite points L*=95, a*=0, b*=0) of the input image data according to thevalue of L*a*b* of the input image data converted by the color spaceconversion section 11 and the height information (color difference)about the embossed image.

The color difference ΔE* can be determined from the followingexpression. Color difference ΔE*=((95−L*)²+(0−a*)²+(0−b*)²)^(1/2)

The height ratio T % (percentage (%)) of the color difference ΔE* valueof the input image to a range (e.g., ΔE*0 to ΔE*n) of the value whichcan actually be possessed by the height information (color difference)about the embossed image is calculated from the value of colordifference ΔE* of the input image data calculated by the aboveexpression.

For example, when it is assumed that color difference ΔE* of the inputimage data is calculated as ΔE*1 by the thermal expandable toner densityconversion section 12 and a range of the value which is actuallypossessed by the height information (color difference) about theembossed image is ΔE*0 to ΔE*n, the height ratio T %1 (percentage (%))of the color difference ΔE*1 value can be calculated as follows.

 T % 1=((ΔE*1−ΔE*0)/(ΔE*n−ΔE*0))×100

The thermal expandable toner density conversion section 12 stores, forexample, Table 1 as shown in FIG. 3A which corresponds the height ratioT % with the thermal expandable toner density H %. And, the thermalexpandable toner density H % corresponding to the height ratio T % ofthe color difference ΔE*1 value calculated by Table 1 can be calculated.

When the height ratio T % of the color difference ΔE* value of the inputimage data is calculated, the subsequent processing is the same asEmbodiment 1 and performed to determine the thermal expandable tonerdensity H % according to the color difference ΔE* of the input imagedata (sRGB) to form an embossed color image having desired height andcoloration.

Embodiment 4 according to the present invention determines theexpandable toner density H % according to chroma (C*) of the input imagedata (sRGB) to form an embossed color image having desired height andcoloration.

The chroma (C*) can be indicated by, for example, distance (chromaC*)=((0−a*)²+(0−b*)²)^(1/2)=(a*²+b*²)^(1/2) from origin points a*=0, onan a*b* plane excepting the value of L* of the L*a*b* color space to thea* value and b* value of the input image data (sRGB).

Embodiment 4 is the same as Embodiment 3 except that the colordifference ΔE* value of the input image data (sRGB) of Embodiment 3 isreplaced with a chroma C* value and the chroma C* is calculated by theabove conversion expression. Therefore, its description is omitted.

Embodiment 5 according to the present invention determines theexpandable toner density H % according to gray scale GS of the inputimage data (sRGB) to form an embossed color image having desired heightand coloration.

Generally, the gray scale GS changes brightness of the image for eachgradation by using white and gray of the input image data (sRGB).

Embodiment 5 is the same as Embodiment 1 except that the signal of theinput image data (sRGB) is converted to gray scale GS and the heightratio T % of the value of the converted gray scale GS is calculated.

The procedure to convert from the input image data (sRGB) to the grayscale GS and to calculate the height ratio T % of the value of theconverted gray scale GS will be described with reference to FIG. 1.

The input image data (sRGB) on each pixel input from an unshown personalcomputer or the like has the value of gamma-corrected RGB and the heightinformation (gray scale) about the embossed image input to the thermalexpandable toner density conversion section 12.

The thermal expandable toner density conversion section 12 converts thevalue of RGB of the input image data which is converted by the colorspace conversion section 11 to the value of gray scale GS by thefollowing conversion expression:

GS=0.3×R+0.59×G+0.11×B

R, G and B in the conversion expression of the gray scale GS indicatethe values of R (red), G (green) and B (blue) having the input imagedata (sRGB) signal gamma-corrected.

When it is assumed in the thermal expandable toner density conversionsection 12 that the value of the gray scale GS of the input image datais GS1 and a range of the value which can actually be possessed byheight information (gray scale) about the embossed image is, forexample, GS0 to GSn, the height ratio T % (percentage (%)) of the valueof gray scale GS of the input image data can be calculated as follows.

T %1=((GS1−GS0)/(GSn−GS0))×100

The thermal expandable toner density conversion section 12 stores Table1 as shown in, for example, FIG. 3A which corresponds the height ratio T% with the thermal expandable toner density H %. Therefore, the thermalexpandable toner density H1% corresponding to the height ratio T % ofthe gray scale GS value calculated using Table 1 can be calculated.

When the height ratio T % of the gray scale GS is calculated, thesubsequent processing is the same as in Embodiment 1 and can beperformed to determine the expandable toner density H % according to thegray scale of the input image data (sRGB) to form an embossed colorimage having desired height and coloration.

Embodiment 6 according to the present invention designates whether theembossed image is formed or the embossed image is not formed from theinput image data signal as the height information designated by the userand forms an embossed image or an ordinary image (ordinary color printimage which is not embossed) according to the designated information.

For example, when the user designates the formation of an embossed imageas the height information, Embodiment 6 sets the thermal expandabletoner density H % to, for example, a maximum amount (100%), and when theuser designates no formation of an embossed image as the heightinformation, and the height information is binarized to form an image bysetting the thermal expandable toner density H % to 0%.

Embodiment 6 is the same as Embodiment 1 except that, when the userdesignates the formation of an embossed image in the thermal expandabletoner density conversion section 12 in Embodiment 1 of FIG. 1, thethermal expandable toner density H % is set to 100% according to theinput image data signal and, when the user designates no formation of anembossed image, the thermal expandable toner density H % is set to 0%according to the input image data signal.

As another embodiment, it may be configured that the user-designatedheight information designates only a density of the input image datasignal, a space frequency of the input image data signal and an edgeportion of the input image data signal as an object of the input imagedata signal and a YMCK total sum signal, the thermal expandable tonerdensity H % is set according to the designated height information toform an embossed color image having desired height and coloration.

In the embodiments described above, the thermal expandable toner wasused as an expandable material for description but any material such asink used for ink jet having expandability may be used.

What is claimed is:
 1. An image formation method for forming an imagecontaining an embossed portion of an expandable material on a recordingmedium, comprising: converting height information about an embossedimage which is the image of the embossed portion to density informationused to indicate a density of a non-embossed image which is not raised;and controlling an amount of the expandable material formed on therecording medium according to the converted density information.
 2. Theimage formation method according to claim 1, wherein the heightinformation is a binary value indicating whether the image is raised ornot.
 3. The image formation method according to claim 1, wherein theheight information is converted to the density information by a hostapparatus, and the amount of the expandable material is controlled by animage formation apparatus.
 4. The image formation method according toclaim 1, wherein the height information is set according to brightnessinformation about the image.
 5. The image formation method according toclaim 1, wherein the height information is set according to psychometricchroma coordinates a*, green-red color, of the image.
 6. The imageformation method according to claim 1, wherein the height information isset according to psychometric chroma coordinates b*, blue-yellow color,of the image.
 7. The image formation method according to claim 1,wherein the height information is set according to luminance informationabout the image.
 8. The image formation method according to claim 1,wherein the height information is set according to a color differencesignal of the image.
 9. The image formation method according to claim 1,wherein the height information is set according to chroma informationabout the image.
 10. The image formation method according to claim 1,wherein the height information is set according to gray scaleinformation about the image.
 11. The image formation method according toclaim 1, wherein the height information is set according to densityinformation about the image.
 12. The image formation method according toclaim 1, wherein the height information is set according to color spacefrequency information about the image.
 13. The image formation methodaccording to claim 1, wherein the height information is set according toan edge portion of the image.
 14. The image formation method accordingto claim 1, wherein the height information is set according to an imageobject of the image.
 15. The image formation method according to claim1, wherein the height information is set according to YMCK total sum ofthe image.
 16. An image formation method for forming an image containingan embossed portion of an expandable material on a recording medium,comprising: converting height information about an embossed image whichis the image of the embossed portion to density information used toindicate a density of a non-embossed image which is not raised; andsending the converted density information to an image formationapparatus which controls an amount of the expandable material formed onthe recording medium according to the density information.
 17. An imageformation apparatus for forming an image containing an embossed portionof an expandable material on a recording medium, comprising: aconversion unit which converts height information about an embossedimage which is the image of the embossed portion to density informationused to indicate a density of a non-embossed image which is not raised;and a control unit which controls an amount of the expandable materialformed on the recording medium according to the density informationconverted by the conversion unit.